The present application relates to a planar illumination device performing large surface emission by successively arranging a plurality of unit light guide plates.
In recent years, liquid crystal display panels, advertising panels for indoor and outdoor uses, signboards and the like become larger, and accordingly, larger light guide plates as backlights of these apparatuses are necessary.
However, it is difficult to form one large light guide plate, and the cost of forming the large light guide plate is high. Therefore, a method of forming a large surface light source by successively arranging a plurality of unit light guide plates is considered. In this method, the large surface light source is manufactured more easily than a method using a large light guide plate, and cost reduction is achievable. However, in the case where a plurality of light guide plates are successively arranged to form a large surface light source, when the large surface light source emits light, a very small amount of illumination light is leaked from a connection section between the light guide plates to cause scattering in a boundary surface, thereby a bright line may be generated in the connection section.
As one technique for solving such an issue, for example, as described in Japanese Unexamined Patent Application Publication No. 2007-213951, there is proposed a technique in which thin ends which are connection parts of unit light guide plates are formed in a recessed-and-projected shape parallel to a light emission surface, and a diffusion sheet is arranged on the unit light guide plates, thereby a bright line leaked from a gap between the connection parts is dispersed.